Switching power supply device, integrated circuit, and switching power supply device operation condition setting method

Abstract

To provide a switching power supply device, and an operation condition setting method thereof, wherein it is possible to set an operation condition during an initialization period by adjusting the resistance value of a resistor that grounds an OUT terminal or IS terminal.A switching power supply device includes an oscillator circuit (3) that regulates the switching frequency of a switching element (Q1), a drive circuit (4) that turns (Q1) on and off based on an oscillation signal from the oscillator circuit (3), a condition setting circuit (6), disposed inside a power supply control IC (100) configured to include the oscillator circuit (3) and drive circuit (4), that outputs a condition indicating signal for indicating an operation condition of the switching power supply device, and a control circuit (1) that instructs the condition setting circuit (6) to determine a condition indicating signal within an initialization period immediately after the start of a supply of power to the power supply control IC (100), wherein a first resistor (R1) having an adjusted resistance value is connected to an external terminal of the power supply control IC (100) from which is output a drive signal to (Q1).

Description

TECHNICAL FIELD[0001]The present invention relates to a switching power supply device that has a condition setting function relating to a power supply action, an integrated circuit that carries out a control of the device, and an operation condition setting method of the device, and in particular, relates to a switching power supply device, an integrated circuit, and an operation condition setting method of the device that can easily set function parameters and / or an operation mode.BACKGROUND ART[0002]A switching power supply device is mounted in an electronic instrument such as, for example, a portable telephone or digital camera, and is used for raising or lowering an input voltage, and supplying the voltage to a load. With this kind of switching power supply device, a condition relating to a power supply action is set by various methods in accordance with power supply specifications required by the electronic instrument.[0003]As important parameters, such as switching frequency, ...

AI Technical Summary

Benefits of technology

This invention allows for accurate setting of specific operation conditions during an initialization period without the need for a dedicated condition setting terminal. This is achieved by selecting the resistance value of a resistor connected to the gate terminal of a switching element or the resistance value of a filter resistor connected to an external terminal to remove noise. Additionally, there is no need to supply a large current to the exterior, as when utilizing a VCC pin decoupling capacitor in Japan Patent No. JP-A-2007-73954.

Problems solved by technology

Normally, when the switching power supply circuit is used in an electronic instrument such as a portable instrument, liquid crystal television, or DVD player, of noise emitted from the switching power supply circuit, there is noise that has an adverse effect on another LSI inside the electronic instrument, and noise that does not.

However, there remains a problem in that, in order to apply the invention to a power supply control IC (integrated circuit) including a boost chopper regulator, an additional dedicated terminal to which the frequency adjusting resistor is connected is necessary.

The number of terminals of a power supply control IC for controlling a switching power supply device is limited owing to requests to suppress cost, package area, and the like.

However, in the event that the lineup of the power supply control IC increases for individual electronic instrument power supply specifications, this also leads to an increase in product cost.

In the event that the capacitance value of the feedback pin loop compensation capacitor is set smaller than a value optimal for the stability of the feedback loop, the system becomes unstable and oscillates.

Conversely, when the capacitance value is set larger than the optimal value, response as a power supply system is slow and, for example, it is not possible to recover the output voltage immediately even when the load fluctuates.

Consequently, the capacitance value of the capacitor has a large effect on the response of the feedback system, and there are problems that restrict the design itself of the switching power supply device, such as adjustment of phase compensation being limited or the power supply oscillating abnormally, due to a change of the capacitance value.

Consequently, a problem with cost occurs.

However, even when the VCC pin decoupling capacitor is charged by a constant current in this kind of connection condition, it is not possible to determine whether charging is done by a current from the external power supply, or whether charging is done by a constant current generated in the power supply control IC.

JP-A-2007-73954 utilizing a multi-functional capacitor, there are problems in that the multi-functional capacitor is difficult to use because the normal function is directly affected, it is necessary to provide a large scale regulator which leads to an increase in cost, the method may not be applicable depending on the method of supplying the VCC voltage, and the like.

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